Papers by Keyword: Deceleration

Abstract: The paper established real-time computing algorithm of S Curve to control the process of acceleration and deceleration for step motor on the basis of a reasonable start frequency. Moreover, this paper used economic embedded ARM STM32F103RCT as the main control chip to control the step motor, which realized this designed real-time computing algorithm. Finally, the relevant testing indicated that the algorithm can realize the rapid response of start and stop for step motor, and can effectively avoid undesirable phenomenon of step losing, overshoot and oscillation.

Abstract: The paper investigates the effects of mechanical wheel slide protection devices (WSPD) on the braking capacity for coaches equipped with disc or cast iron block brakes. Decelerations and jerks, that affect the passengers comfort, are also analyzed. An original simulation program, based on experimentally determined air pressure evolutions in brake cylinder is used for this purpose. Results of numerical simulations show that in the case of repeated actuations of mechanical WSPDs, disc brake vehicles are more affected in terms of braking capacity. Regarding jerks during braking actions, in both normal and low adhesion conditions, vehicles equipped with high power cast iron block brake with two pressure levels prove to be more affected.

Abstract: Considering the diversity and random of the factors in traditional safety distance model, the deceleration and some time parameters in the braking action of the modified model were quantified first. When the following car moved slowly than the car ahead, it usually tailgated with speed modes. This case was considered in the modified safety-distance model. The model is proven to be higher accuracy by calculating and emulation analysis. Research shows that smaller speed difference, less the safety-distance it needs to keep, but it becomes insignificant when the following car is slower than the car ahead. There is greater uncertainty in rear-ending accidents for overlooking the fact that the car following with speeding in the traditional model.

Abstract: The final process of workpiece is composed of a series of connected trajectories, and the expectation speed of the different trajectories may be different, so it requires the changes of acceleration and deceleration speed. This paper introduces the improved acceleration-deceleration algorithm of trigonometric function, and presents an optimization algorithm according to the changing trend of velocity to the method of forward-looking processing speed.

Abstract: The concrete under penetration has a restricted deform and is in intrinsic friction state. By used conservation of mass, conservation of momentum and velocity expression on wave front, the velocity field of the pulverized zone near penetration is obtained. The boundary conditions and the continuum conditions were also considered for the obtained velocity field. The pulverized concrete near the penetration is described by Mohr-Coulomb criterion. Based on the conclusions above, cavity expand theory and the expand equation of inconsistent deform, the resistance of projectile is gained in intrinsic friction state. In according to movement differential equation, the deceleration model is built which can describe different phases for penetration and perforation. The decelerations of different size projectiles with different velocity were calculated and were contrasted with experimental data.

Abstract: The emergency braking deceleration and braking distance of high-speed train were studied under the conditions of adhesion brake on dry and humid rail surfaces, and adhesion and non-adhesion composite brake on humid rail surface. The average emergency braking deceleration was calculated by the area-method. The results show that the braking performance is affected significantly by the wheel/rail adhesion state and the braking performance of high-speed train can be improved by applying the adhesion and non-adhesion composite brake in the state of humid rail surface.

Abstract: This paper proposes coupling the Pipes car-following model with the GM model to formulate a new car-following model that can generate consistent separation distances between the leading and following vehicles. First, an example is given to show that the GM car-following model can lead to different separation distances at the same steady speed. Secondly, a new model is formulated by coupling the Pipes model with the GM model and it is shown that the only meaningful attractor of the new model is one producing consistent separation distances at the same steady speed. Furthermore, the relationship of those macroscopic traffic flow quantities inherent in the new car-following model has also been investigated. In the steady state, the resulting speed-density relationship is exactly the same as one derived from the Pipes model. In the dynamic case, the derived speed-density relationship is a partial differential equation. Numerical experiments are carried out to show that the new car-following model can generate consistent separation distances between the leading and following vehicles.

Abstract: A new method of sampled-data S-curve acceleration/deceleration for industrial robots and CNC machine tools was put forward, which can deal with the low velocity zone called “tail” in a deceleration zone. The equations of acceleration and deceleration were detailed, which improved the productivity by avoiding the calculation of the deceleration point at every sampled time. According to the distance of the trajectory, the trajectory can be divided into normal block, short block I type and short block II type. Aiming at each block, the equations of distance, acceleration, velocity and Jerk were given and the discrete equation of each method was presented. We have implemented our algorithm in both simulation environment and real CNC systems and conducted a series of experiments. The experimental results demonstrate that the proposed method is effective.

Abstract: The paper proposes an algorithm for control of processes based on variable-speed drives with low acceleration and deceleration rate of the motor, which determines the dynamics of the whole control system. The results of investigation of the controller based on the proposed algorithm are presented and discussed. The controller provides good transient performance of the control system response in case when the drives with different motor acceleration and deceleration rates are used.

Abstract: To guarantee the efficiency and accuracy of machining in high speed machining, a novel vector blending algorithm for velocity smooth link is proposed. Based on efficient acceleration/deceleration technique for a single distance movement, the desired acceleration/deceleration characteristics can be selected. According to acceleration/deceleration characteristics, two different acceleration/deceleration profiles for two corresponding distance movements are constructed respectively. Under the condition of length of movement, highest velocity and direction of motion, two different acceleration/deceleration profiles are blended. On-line implementation results show that the proposed approach makes velocity link smoothly and efficiency and accuracy of machining can be guaranteed.